A private Taiwan research institute's proposal to rewrite the island's constitution has provoked a heated response from a Chinese official, an indication of how sensitive Beijing is to the slightest hint that Taiwan might be moving toward formal independence. Daniel Schearf reports from Beijing.

The proposal comes from the Taiwan Thinktank, a private research institute that favors Taiwan's independence from China.

It calls for the establishment of a "second republic" to reflect the current political reality, and to enhance the island's distinct identity.

Taiwan still calls itself the Republic of China, the official name of China until the Nationalist government was pushed out by the Communist Party in 1949 and fled to Taiwan for safety.

For decades, the Nationalists maintained that they were the legitimate government of all of China. The reality is that the communist government is firmly in charge of the Chinese mainland, which is known as the People's Republic of China. As the constitutional proposal notes, the Taiwan government rules only Taiwan itself and several smaller islands.

The proposal, which calls for a referendum on constitutional change, is one of about 15 currently circulating in Taiwan. While Taiwan President Chen Shui-bian has indicated he favors rewriting the constitution before he leaves office, neither this proposal nor any of the others is on the official agenda at this time.

Nevertheless, at a briefing by the mainland's Taiwan Affairs Office Wednesday, spokesman Yang Yi let loose a blast at the proposal, and linked it to President Chen's known support for independence.

"This so-called 'second republic' draft constitution caters to Chen Shui-bian's conspiracy to seek legal Taiwan independence, and brazenly incorporates the secessionist position of 'one country on each side," he said.

China claims democratic and self-ruled Taiwan is a runaway province, and says it must eventually be reunited with the mainland, through diplomacy or the use of military force.

While trade relations across the Taiwan Strait have blossomed, political ties become strained any time there is the slightest hint that the island might be moving toward formal independence.

After warnings from Beijing and Washington, Mr. Chen has muted his talk of independence, but he loses no opportunity to assert Taiwan's separate identity. Last month, he angered Beijing by supporting the removal the word "China" from the names of Taiwan's government-owned companies.

His government has also supported moves to change school history textbooks to place less emphasis on China's history, and more on Taiwan's.

The United States, like most countries, supports the so-called "One-China" policy, but has also vowed to defend Taiwan in the event of an attack by the mainland.

Beijing has condemned Taiwan's plans to buy missiles and jet fighters from the United States, labeling it as interference in China's "internal" affairs.